Spontaneous interface engineering for dopant-free poly(3-hexylthiophene) perovskite solar cells with efficiency over 24%

Halide perovskite solar cells (PSCs) have recently shown a leap forward in performance by reducing the recombination loss at the interface between the perovskite and hole-transporting layers through surface treatment. However, additional surface treatment processes such as spin-coating or annealing are undesirable for commercialization in terms of the production cost. In addition, commonly used organic hole-transporting materials (HTMs) such as 2,2′,7,7′-tetrakis[N,N-di(4methoxylphenyl)amino]-9,9′-spirobifluorene (spiro-OMeTAD) and poly(triarylamine) (PTAA) are used with hygroscopic additives, which deteriorate the long-term stability and hinder the commercialization of PSCs. Herein, we report an efficient strategy for interface engineering by directly incorporating gallium(iii) acetylacetonate (Ga(acac)3) into HTMs without subsequent processes and hygroscopic dopants. The incorporated Ga(acac)3 spontaneously interacts with the surface of the perovskite layer, yielding a reduction of the interfacial recombination loss for various organic HTMs. In particular, by applying Ga(acac)3 in poly(3-hexylthiophene) (P3HT), the PSCs showed a significant improvement in the power conversion efficiency (PCE) from 17.7% for the control device to 21.8%. The Ga(acac)3-devices also showed superior moisture stability for 2000 hours under 85% relative humidity at room temperature without any encapsulation, maintaining a complete initial performance. We also demonstrated that the incorporated Ga(acac)3 successfully works on the best-known PSCs with the aligned P3HT, showing an enhanced PCE of 24.6%. We believe that this work presents a route for the high performance and commercialization of PSCs.